Global Positioning System Satellites

A stream of highly charged particles from the sun is headed straight toward Earth, threatening to plunge cities around the world into darkness and bring the global economy screeching to a halt. This isn't the premise of the latest doomsday thriller. Massive solar storms have happened before - and another one is likely to occur soon, according to Mike Hapgood, a space weather scientist at the Rutherford Appleton Laboratory near Oxford, England. Much of the planet's electronic equipment, as well as orbiting satellites, have been built to withstand these periodic geomagnetic storms.

The launching of an Air Force Delta 2 rocket carrying a $65-million military navigation satellite was postponed at least 24 hours because of trouble with a second-stage fuel pressurization system, officials at the Kennedy Space Center in Florida said. It was the nation's second major launching delay in three days. The maiden flight of a commercial Titan 3 rocket was rained out Friday. Officials said it was not known how long it would take to make the Delta repairs.

An unmanned rocket carrying a $40-million navigation satellite for the Air Force blew up 13 seconds after liftoff Friday in a spectacular cascade of flaming debris. Nearly 200 people had gathered at two viewing sites, one of them less than a mile from the Cape Canaveral Air Force Station launch site. In addition, 73 launch team members were in the blockhouse next to the pad.

The Air Force, acting with unusual speed to respond to the space launch crisis in the wake of the loss of the space shuttle Challenger, on Friday awarded four design contracts worth about $5 million each to aerospace firms proposing new launch vehicles. Hughes Aircraft, McDonnell Douglas Astronautics and General Dynamics Convair, all Southern California firms, received contracts, as did Martin Marietta's Denver Aerospace.

Tracking traffic can be an expensive business. In some places, costly cameras and radar systems are mounted high above highways to watch traffic at strategic points. Transportation agencies also dig up roads to install sensors that monitor the flow. And helicopters roam the skies of the busiest cities, relaying information on the choked roadways to media outlets.

A Rockwell International division in Seal Beach has lost to General Electric a $1.2-billion contract for the second phase of an Air Force satellite program that the company has worked on since 1983. An Air Force official close to the program said a Rockwell scheme to overcharge the government on the first phase of the work apparently contributed to the loss of the contract. A Rockwell official, however, denied that its overbilling conviction figured in the Air Force's decision.

A former executive for Rockwell International Corp. pleaded guilty Monday to charges that he schemed to double-bill the Air Force by nearly $450,000 on contracts for a satellite navigational system. Robert L. Zavodnik, 46, of Fountain Valley, a former material subcontractor manager at Rockwell's space division in Seal Beach, pleaded guilty to one count of conspiracy to make false statements and one count of making false statements.

Astronauts aboard the space shuttle Discovery on Thursday tried out an Army laser receiver and a new camera system designed by the Navy, but poor weather conditions hampered their efforts. The five military crew members began work on the unclassified portion of their weeklong mission after successfully releasing a spy satellite for the Pentagon on Wednesday. The laser receiver and camera are intended to eventually assist in warfare.

Trying to monitor molten rock deep within the Earth, scientists from the United States and Mexico are looking to the skies for help. Geologists are expanding a network of detectors that monitor Global Positioning System satellites to try to determine if the Popocatepetl volcano is expanding or contracting. That could help determine if it is likely to explode. "The logistical difficulties are huge," said Tim Dixon of the University of Miami. "It's high up. It's cold. It's dangerous.